Safety tool for supporting and holding at least one interchangeable utensil, particularly on a press-bending machine

ABSTRACT

Safety tool for supporting and holding an interchangeable utensil, which includes a holding clip, hinged to the utensil support body joined to the beam, the said clip being pushed on one side, while on the other side there are teeth facing the utensil support body, and of which a tooth is used for holding a safety hook and a lower tooth presses against the outer side of a spring for lifting the hook. The safety hook, being positioned between the holding clip and the utensil support body, has a seat on one side, along which the said first tooth of the holding clip is inserted, while on the other side, there is a hooking terminal with a leading plane, that is inserted inside a groove, preferably of the type for utensils with a standard shank.

[0001] This application is a continuation of pending International Application No. PCT/IT00/00473 filed Nov. 22, 2000, which designates the United States and claims priority of Italian Patent Application No. 99A0001 34 filed Nov. 30, 1999.

FIELD OF THE INVENTION

[0002] The object of the invention contained herein is a safety tool for supporting and holding a utensil in a clamping system, used on the upper beam of a press-bending machine.

[0003] The invention has particular, but not necessarily exclusive, application in the press-bending machines sector.

BACKGROUND OF THE INVENTION

[0004] There are various types of press-bending machines. They are used in the mechanical engineering industry, particularly for processing sheets of metal in order to obtain, for example, longitudinal sections with various profiles that can be re-worked with a press-bending cycle.

[0005] A press-bending cycle consists basically in a bending tool that moves down vertically until it presses on the sheet of metal that is positioned on a work-bed, carries out the bending of the sheet and returns to its original position. To carry out the aforementioned phases, the machine is made up of two parts. The first part is mobile which is usually the upper part of the machine, and a lower part that is static and positioned perpendicular to the upper part. Regarding the mobile part, during a typical work cycle the utensil, made of an interchangeable blade shaped according to the work to be carried out, carries out a vertical return movement by means of a hydraulic cylinder on the end which determines the lowering of an upper beam that, by holding the said utensil in a clamping system, carries it towards a lower beam on which an interchangeable mould is positioned, followed by a pause and its return upwards to the original position.

[0006] State of the Art

[0007] Generally speaking, most press-bending machines currently available on the market have interchangeable utensils that make the machine more flexible in order to meet the wide range of requirements for the companies that use them.

[0008] According to the type of work to be carried out on the sheet of metal, there are two types of utensil. The first one is made up of a single utensil, that is, a single monolithic body with a linear blade, which is held longitudinally along the entire length of the upper beam by means of a single clamping system. The second type is made up of a divided or multiple utensil, with various elements held by clamping systems to the upper beam. Each element is a single utensil and they may even be different from each other. While with the first type a single, continuous type of clamping system along the length of the upper beam is required to hold the utensil, with the second type a number of intermediate clamping systems are required according to the number of single utensils to be held and clamped.

[0009] Regarding the utensil itself, both parts are usually made up of a one-piece metallic body, with a square upper part called the shank, and a lower part that can be of various shapes, called the punch. The shank is for attaching the utensil to the upper beam, and it is the part on which the clamping systems operate. The said systems, operated by pneumatic or hydraulic cylinders, or other means of electromechanical systems, close one or more plates with a large surface area, each one clamping and holding the shank of the utensil.

[0010] The utensil or utensils have to be replaced more or less frequently, according to the type of work being carried out on the sheet of metal in question. This operation has to be carried out with the machine in a temporary state of arrest, and preferably with the upper beam at an accessible working height for the operator, to make the operation simpler.

[0011] To sum up, (see FIGS. 3, 3A and 3B that represent typical applications), whatever the shape of punch or punches used, there are three types of shanks available on the market that are clamped by one or more clamping means to the upper beam:

[0012] The original type of shank, as shown in the attached figure, and indicated with Cl. This solution has been abandoned by all the manufacturers because of its lack of safety features. This type of shank has only one tooth that is square to both sides and the smooth walls. There is a support surface for the utensil adjacent to the tooth, for example on the head of an intermediate on which the pushing force is distributed perpendicularly.

[0013] Standard-type shank C2. This type, for punches with a pressing axis that is not in line with the support shank, has been standardised by all constructors of press-bending machines and utensils and, compared to the first type, is characterised by the fact that it has a certain safety feature. This feature is made up of a seat or “C”-shaped continuous groove which runs transversally to the utensil at the base and on one side of the shank, on the inside of which a holding tooth enters along the intermediate. The main function of this feature is to avoid the utensil dropping from its seat when the clamping means along the intermediate are released. A variation of the standard shank with a single safety fitting has a double safety groove. In this case, on each of the two sides of the shank of a utensil with the shank in line with the respective punch, there is a groove which runs transversally, similar to the groove used for a single-type safety shank.

[0014] The third type, which is not as common as the second type, is indicated with C3, and is only produced by some manufacturers. These “personalised” shanks are designed to be used exclusively on certain makes of press-bending machines and are not interchangeable with other machines. A typical example is the GASPARINI® shank which, compared with the previous examples, is characterised by the fact that it has a wedge-shaped groove, into which the tooth of the clamping means enters and that, when released, allows the shank to be suspended from the upper beam in complete safety until it is manually removed by the operator.

[0015] Drawbacks

[0016] From the brief description above, it easy to imagine the main problems that the producers are trying to solve. First of all, there is the problem of the time required and the difficulties encountered when carrying out the operation of replacing the utensil. Especially when using the utensil C2, which is the type most widely used, the operator has to withdraw the utensil along one side. This operation is relatively simple if there is enough space at the side of the machine and if there is only one utensil to be drawn out from the upper beam. The utensil may be quite heavy, thus requiring more than one operator to withdraw it, or may require suitable lifting means such as a winch. The operation becomes much more difficult if the utensil is divided. In this case, when the distance between the intermediates is less than the length of the utensil, it is necessary to draw it out by withdrawing all the utensils that precede it, with all the problems that are inherent with this type of operation.

[0017] All these operations have to be carried out with the machine in a rest position, which obviously implies that the cost involved will be proportional to the number of interventions that have to be carried out.

[0018] A second aspect that cannot be overlooked is the fact that the utensils with safety features currently used are not automatically aligned. This problem is quite serious when high-precision components are being manufactured and where the split utensils have to be perfectly aligned with each other. With the current technology, this condition is almost impossible to reach, with the result that the operations carried out on the sheets of metal positioned below the utensil are not satisfactory according to current standards.

[0019] Amongst the solutions commonly used in order to resolve the first of the problems mentioned above, that is withdrawing the utensil sideways with respect to the upper beam, the insertion of the utensil from below, and vice versa for its removal, is becoming common practice. In this case, in order to hold the groove of the safety feature that runs transversally to the standard-type shank, a wedge is used that is pressed into position in the groove by a spiral spring. This solution requires a considerable amount of effort by the operator to overcome the force of the spring, both when inserting or withdrawing the shank of the utensil from the clamping means on the upper beam. The main drawback is given by the fact that the spring must be very strong in order to hold the utensil in place when it is released, and must provide a strong pushing force perpendicular to the groove.

[0020] What is more, regarding the technique described, the force of the spring has to be calculated according to the length of the utensil in order to make its movement easy. It is precisely the calculation of the force of the spring that presents a number of problems regarding the setting-up of this mechanism.

[0021] There is also a system that is defined as “self-aligning” by the manufacturer. This system has a closing plate with an inclined plane at the end that is tangential to the top of the side of the groove in the shank of the utensil. When the plate is brought close, the plane goes against the top of the said side, forcing the utensil to go along the diagonal. Even though this solution seems original, it can only be used for utensils made up of one single element, while in those cases where divided utensils are used, it does not guarantee a uniform anchorage of all the elements, leaving play and leading to misalignment of the utensils, which obviously leads to poor quality processing.

[0022] U.S. Pat. No. 5,022,256 Discloses a safety tool having the feature stated in the precharacterising portion of claim 1. It provides a faible resilient strip (6,32) having the hooking tooth (11 ) for safety purposes.

[0023] EP0779116A (AMADA GMBH), FIG. 2 discloses a quick clamping device for at least one tool (utensil in the description) of a machine tool, in particular for one bending or edging punch of a bending or edging press, comprising a clamping member and a safety and hold means for the tool (utensil), said clamping member being provided with an engagement strip which is pre-tensioned for engagement with a counter-recess in the tool shank and which is attached to be actuated by a central operating member in direction opposite to its pretension. The above solution provides the use of an intermediate tool-engaging means (4) between the press-bending up-down-moving upper support (2) and said bending tool or punch (utensil) and having the features of: hand-operated; missing in in-line tool; unlocked positioning means in case of different thickness; dangerous in tool extraction because one hand must be under the tool.

[0024] FR2339485A (COLLY PIERRE) discloses a lever hooking and locking means for a safety tool to be clamped as a solution close to the previous one. This feature not providing high-precision and self-alignment and providing: use with personalized bending-tools (puches) and side insertion only.

[0025] FR26916524 (TREILLET JEAN) discloses a safety tool device directly connected to the upper press-bending support, without intermediate locking safety device. This feature being manual with personalized tools (punches). Realization requiring a very high precision. Recovering in thickness being missing.

[0026] In the lever means solutions disclosed in EP0779116A and FR2339485A, a lever hooking and clamping means is disclosed, said lever hooking and clamping means has the fulcrum on the upper end, clamping action being operated closing said lever means by acting on an intermediate portion of it, by an intermediate closing screw (in the EP0779116A Ref, 7,8 and in the FR2339485A

[0027] Ref.3-6 assisted by side-counter-springs 7): In this way making operative the hooking of the bending-tool or punch or utensil, but with a force that is ½ of the closing force in its intermediate portion.

[0028] With regard to the above, and other techniques that are less widely used, the applicant believes that the means for holding the utensil can be greatly improved with regard to operator safety.

BRIEF DESCRIPTIONS OF THE INVENTION

[0029] This and other aims are achieved with a safety tool having the features according to claim 1.

[0030] Dependent claims being directed to different advantageous solutions.

[0031] Advantages

[0032] In this way, through the creative contribution of the system which leads to an immediate technical progress, various advantages are achieved.

[0033] In particular, the safety tool mechanism for holding the utensil is extremely flexible since it can be applied to the upper beam on any press-bending machine currently used. It is extremely efficient and functional because it can be applied in all those situations where intermediates used for clamping standard safety shanks are foreseen.

[0034] Going into detail, there are considerable advantages for the operator of the machine, who can carry out removal of the utensil from the upper beam in complete safety with a very simple operation that, above all, allows the operator to perceive the moment in which the utensil is unhooked and released from above to below slightly in advance. At the same time, the insertion of the chosen utensil in the intermediate positions along the beam from below can be performed, an operation which can be carried out very quickly and without any particular effort by the operator.

[0035] Regarding safety, each utensil is moved laterally using either one or both hands, and not as in the previous systems, along the line of the press, thus offering maximum protection against work accidents.

[0036] Among the advantages that are worthy of note, there is an unrivalled self-aligning capacity of each utensil with the other split utensils along the horizontal and vertical axes when using this system, so that extremely precise pressing operations can be carried out and thus considerably improving the overall quality of the finished product.

[0037] The elimination of play and the stability of the utensil after closing the holding clip further improve the quality of the process. The said system, right from the initial contact with the sheet of metal to be processed, eliminates the small movement along the vertical axis of the utensil that is perceived when using traditional clamping systems. Furthermore, since the system has no play, the operator has an impression of working with a reliable tool, thus leading to a natural sensation of operating under safe working conditions.

[0038] The overall safety is considerably improved since the utensil, when released, can not fall even if it oscillates laterally, whether in one direction or another, as may accidentally occur in the systems described previously.

[0039] Because of the presence of the hooks, which are more or less equal in length to the intermediate pieces, the utensil is hooked more safely because, if one or more of the hooks are no longer operational, there are the remaining hooks that hold the utensil very efficiently.

[0040] Furthermore, because of the adoption of certain measures, there is a uniform holding of the utensil, which is distributed evenly along all the surface of the shank of the utensil. At the same time, by modifying the mechanism for operating the holding clip, the hold is also more uniform when only one clamping system is used to clamp a single utensil to the upper beam.

[0041] These and other advantages will be explained in the following detailed description and attached drawings of various applications of the system, which are to be considered simply examples and not limitations of the system.

BRIEF DESCRIPTION OF THE DRAWINGS

[0042]FIG. 1 is a side view of the assembly of a self-aligning set for holding intermediates under pressure, and without a utensil.

[0043]FIG. 2 is a side view of the assembly of a self-aligning set for holding intermediates at rest, and without a utensil.

[0044]FIG. 3 is a view of a utensil shank with a standard safety fitting.

[0045]FIGS. 3A and 3B show two other types of utensil shanks for reference purposes.

[0046] FIGS. 4 to 7 show the sequence for inserting the utensil from below towards at least one upper intermediate.

[0047] FIGS. 8 to 10 show the sequence for holding the utensil shown in the previous figures.

[0048] FIGS. 11 to 15 show the sequence for releasing and removing the utensil shown in the previous figures.

[0049]FIGS. 16 and 17 are schematic views of the sequence of the most important phases of the mechanism, and in particular the operations relative to the holding of the utensil against the intermediate, with the first sequence showing the vertical raising of the utensil, and the second phase in which the utensil, when it reaches its stop, is pushed laterally by means of the spring that presses the hook.

[0050]FIGS. 18 and 19 show various ways of applying the safety system to the intermediate in a multiple version, in the first two cases to hold utensils with shanks that are not axial and with the punch mounted at the front or the back.

[0051]FIG. 20 shows a mixed application of the system with the use of the aforementioned safety system on one side and, on the other side with respect to the intermediate, a traditional plate that is blocked manually.

[0052]FIGS. 21 and 22 show application variations of the safety system, respectively: an adapted piece for the intermediate with a central attachment and utensils with central attachments of the type with a shank that is symmetrical with respect to the load axis (FIG. 21); an adapted piece for the intermediate with an attachment that is not axial with respect to the load axis for a utensil with a central attachment of the type with the utensil shank that is symmetrical with respect to the load axis (FIG. 22). FIG. 24 represents an explosion view of the system.

DESCRIPTION OF TYPICAL APPLICATIONS OF THE INVENTION

[0053] By referring to the illustrations, it can be said that a pressbending machine is made up of an upper part and a lower part. The upper part is mobile while the second part is static. In the first part, there is an upper beam that moves along a vertical axis and which, longitudinally, by means of an intermediate set (A) with a self-aligning holding mechanism, holds an interchangeable utensil (1).

[0054] The utensil (1) is made up of a metallic monolithic body, which, on the lower end, makes up the punch (11) used for pressing against the sheet of metal. On the upper end there is a shank (12) with a “C”-shaped (13) groove along one side (122), which acts as a safety device. Going further into detail, the shank (12) of the utensil (1) can be either non-axial (see FIGS. 1 to 2 and 4 to 17) or axial with respect to the load axis, as shown in FIG. 21.

[0055] A first example foresees an intermediate set (A) made up of a metallic body (2) with an attachment (21) to the upper beam of the press-bending machine on the upper side. The lower part of the said intermediate body (2) has a vertical reference plane (22) along which, in taking up the utensil (1), the corresponding flat surface on the side (121) of the shank (12) is positioned.

[0056] Halfway along, the intermediate body (2) has a chamber under pressure (23) in the case of a pneumatic type, which pushes and draws back a piston (3) with a perimeter seal (31). The purpose of the said piston (3) is to act upon the upper end (42) of a holding clip (4), which, by means of jointed screws (5), is hinged to the body of the intermediate (2). The aim of the holding clip (4) is to transfer the push of the piston (3) to the lower end (41) of the holding clip, which on the inner side has a particular conformation.

[0057] Going further into detail, the said lower end (41) of the holding clip (4) has at least two longitudinal parallel teeth (411) and (412) which face the same side. The upper tooth (411) has a groove (413), on the inside of which the upper portion (61) of a intermediate safety hook (6) is inserted. The second (412) of the two teeth, with both of them facing towards the body of the intermediate (2), coincides with the lower edge of the holding clip (4). This tooth (412) is similar to a half round lip which sticks out towards the surface (22) of the body of the intermediate (2). The purpose of this tooth (412) is to press on the outer side of at least one spring (7) for lifting the hook (6), the said spring having a “V”-shaped conformation. The said spring (7) is made of spring steel and partially overlaps and joins, by straddling, a corresponding male protrusion (63), which serves as a body, transversally formed into the intermediate safety hook (6). Between the said spring (7) and the back (63) of the hook (6) there is a certain amount of play, so that the spring (7), when acted upon by the tooth (412), is deflected in a controlled manner, thus guaranteeing the hook's (6) adherence to the shank of the utensil, and its pressure against the body (2) of the intermediate.

[0058] Finally, there is at least one intermediate safety hook (6). It is positioned between the flat reference surface (22) of the body of the intermediate piece (2) and the lower end (41) of the holding clip (4), and is partially involved by the positioning of the lifting spring (7) of the hook (6). The conformation of the intermediate safety hook (6), which is made up of monolithic metallic body, is formed in such a way as to have two symmetrical spikes (61) along the upper side, that stick out and face the holding clip (4). The two spikes (61) temporarily act upon the holding clip (4) by sitting inside the groove (413) formed along the respective tooth (411). Below the spikes, there is the body (63) facing the same side which supports, in a straddling fashion, the spring (7), leaving a certain amount of space between the two surfaces in order to allow the spring a certain amount of movement to adapt itself when acted upon by the end (412) of the holding clip (4). On the opposite side, that is on the surface of the intermediate safety hook (6) facing the surface (22) of the body of the intermediate (2), a main tooth (62) is formed which also has a hooking function, and with a flat reference and lifting surface (621) and an inclined surface that acts as a lead for the movement (622). In a preferred solution, the intermediate safety hook (6) has a an O-ring (64) partially embedded in a respective seat (641) which is formed opposite the protruding body (63) on the side facing the surface (122) of the shank (12) to be clamped. One of the aims of the said O-ring (64) is to guarantee that split utensils are well fitted, by compensating for play due to wear of the shank (12) or imprecise manufacturing.

[0059] Finally, on the top of the intermediate safety hook (6) there is another small tooth (66) that faces the clip (4), which works in conjunction with a catch (414) on the surface of the said holding clip (4). The purpose of this arrangement is that, in conditions where the clip (4) is open with rotation of the utensil (1) (see FIG. 8), even if the utensil (1) is forced more than that of the force of gravity, the intermediate safety hook (6) can not slide upwards. During the release phase of the utensil (1), the aforementioned arrangement guarantees (by rotation according to FIG. 13), that the hook is held high during oscillation.

[0060] Regarding the preferred solution for moving the clip (4), it can be made mobile along the orthogonal axis with respect to the load axis of the utensil along the line of pressing. In this case, there is a series of guides and at least one return cylinder.

FUNCTIONAL DESCRIPTION

[0061] FIGS. 4 to 7 show the phases for inserting the utensil (1) along at least one intermediate (A). going into detail, the operator grips the utensil with at least one hand (H) between the shank (12) and the punch (11). He then pushes it upwards as indicated in FIG. 4 until the external upper edge sits on the inclined plane (622) of the intermediate safety hook (6). By continuing the upward movement of the utensil (1) (see FIG. 5) the head of the shank (12) creates a slight misalignment of the intermediate safety hook (6) with respect to the perpendicular, brought back into line when the upward motion of the utensil is continued until the tooth (62) intercepts the groove (13) along the side (122) of the said shank (12).

[0062] In this position the tooth (62) is lifted and opened, sliding with the surface of the spring (7) along the surface of the lip (412), leaving a space to insert the utensil (1). At this point, the intermediate safety hook (6) goes down due to gravitational forces and goes into the groove (13), leaving a certain amount of play.

[0063] As a result, if the insertion movement is continued, the intermediate safety hook (6) moves back to a perpendicular position to hook the groove (13) with the tooth (62) and pulls the intermediate safety hook (6) and utensil (1) upwards, until the lower end of the intermediate body (2) goes against the base (123) of the utensil (1) from which the shank (12) rises. In this position, the intermediate safety hook (6) is independent from the intermediate set (A), while the side (121) of the shank (12) of the utensil (1) rests against the reference plane (22) of the intermediate body (2). On reaching this phase, the operator may let go of the utensil (1) (see FIG. 7) because, due to gravitational forces, it drops down slightly and pulls the intermediate safety hook (6) down, so that the spring (7) fits along the lip (412) to hold the utensil (1) tight.

[0064] It remains suspended because each spike (61) of every intermediate safety hook (6) is inside the groove (413) of the first tooth (411) formed on the inside of the holding clip (4).

[0065] In this position, if the utensil oscillates in one direction or another (see FIGS. 8 and 9), the particular arrangement of the system keeps the utensil hooked. This specific condition is guaranteed by the presence of the spring (7) joined along one side of the safety intermediate safety hook (6). The spring (7), if the utensil (1) is released in any position, rests pressed on the outside against the lip (412) of the holding clip (4).

[0066] By pushing against the holding clip (4) with the piston (3) (see FIGS. 16 and 17), a movement of the end (41) is indirectly obtained. It presses with the lip (412) against the outside of the spring (7), creating a lifting movement of the utensil (1), until the base (123) of the utensil (1) adjacent to the shank (12) rests against the lower side of the intermediate body (1). In this way, the shank is tightened (see FIG. 10).

[0067] The illustrations that follow (FIGS. 11 to 15) show the release phases of the utensil (1) from the intermediate group (A). In particular, by releasing the pneumatic command, the holding clip (4) opens and releases the utensil (1), which drops down due to gravitational forces and is held by the intermediate safety hook (6). The operator then holds (H) the utensil (1) and pushes it upwards until the tooth (65) is intercepted, an action that pulls the intermediate safety hook (6) and releases it from the holding clip (4). This is followed by a rotational movement towards the body of the intermediate (2) using the edge of the lower side of the body of the intermediate (2) as a fulcrum, on which the rotation of the utensil (1) is carried out. In this way, the outer edge of the head of the shank (12) acts on the intermediate safety hook (6) again and moves out of line and, as a consequence, preliminarily releases the hook (62) from the groove (13). To complete the extraction of the utensil (1), it must be held in a temporary rotational and lowering condition, until the fulcrum on which the movement pivots goes from the flat (123) to the side (121). By continuing with the pulling force downwards the extraction operation is completed.

[0068] The system described above can also be used for a variation, which is often found in the intermediates for gripping the utensil. In particular, this is the A1 type of intermediate, which has a multiple attachment for the utensil (1), in this case two, one for each side of the upper beam. These intermediates, shown in FIGS. 18 and 19, have two mirror-image holding systems and at least one holding clip (4) on each side of the upper beam, which acts upon at least one corresponding intermediate safety hook (6) by means of a spring (7) placed in between for lifting the hook, joined to the said intermediate safety hook (6). In this way, at least one utensil (1) can be held on each side, whether fitted to the front or to the back.

[0069] A further variation foresees a mixed intermediate A2 which is another multiple attachment, differing from the previous one in that it has a holding clip (4) on one side only, while on the other side there is traditional mechanical holding system, by means of a fixing plate for the shank (12), with a fixing screw for the intermediate. With this method, the said screw is accessible from the front of the machine to make the operator's work easier (see FIG. 20).

[0070]FIGS. 21 and 22 show another variation to the intermediate set-up. In detail, this is a first intermediate A3 with an attachment on the upper beam which is axial with respect to the load axis of the utensil, and a second intermediate with an attachment on the upper beam which is out of line with respect to the load axis of the utensil.

[0071] With both solutions the utensil (1), with its shank symmetrical to the load axis and with a safety groove (13) on both sides, is held by a clamping unit as previously described, with a holding clip (4) that acts upon at least one corresponding intermediate safety hook (6) by means of a spring (7) for lifting the hook, joined to the said intermediate safety hook (6). The aim of this type of utensil is so that it can be rotated 180°, such as in the case of the utensil shown in FIGS. 18 and 19, without having to use two different attachments. 

What is claimed is:
 1. Safety tool for supporting and holding at least one interchangeable utensil (1), in particular to the upper beam of a press-bending machine by means of at least one clamping means joined to the said beam, wherein said safety tool includes a holding clip (4), joined to the support body (2) of a clamping means for the utensil (1) and wherein said safety tool comprises a safety hook, having on the opposite side a terminal hooking tooth that enters into a groove along the side of the shank of the utensil, characterised in that said holding clip (4) has a series of teeth (411, 412, 414) facing the utensil-shank abutting reference surface (22) of the support body (2) to engage, by an intermediate safety hook (6), the shank (12) of said utensil (1), and of which at least one of the teeth (411, 412, 414) is used for holding said intermediate safety hook (6) in a temporary suspended position, while a second one acts upon the said intermediate safety hook (6), the said intermediate safety hook (6) having at least one seat along the side, and in which at least one tooth (411, 412, 414) of the holding clip (4) fits, while on the opposite side there is a lower terminal hooking tooth (62) that enters into a groove (13) along one side (122) of the shank (12) of said utensil (1).
 2. Safety tool according to claim 1 for supporting and holding at least one interchangeable utensil, in particular to the upper beam of a press-bending machine by means of at least one clamping system joined to the said beam, characterised by the fact that it includes a holding clip (4), joined to the body (2) of a clamping system for the utensil (1) with the said clip (4), being hinged on one side, is acted upon by a pneumatic or hydraulic mechanism, while on the opposite side there is a series of teeth (411, 412, 414) facing the reference surface (22) of the utensil (1) support body (2), and of which at least one of the said teeth is used for holding an intermediate safety hook (6) in a temporary suspended position, while the lower tooth (412) acts upon the said intermediate safety hook (6), the said intermediate safety hook (6) having at least one seat along the side, and in which at least one tooth of the holding clip (4) fits, while on the opposite side there is a lower terminal hooking tooth (62) that enters into a groove (13) along one side (122) of the shank (12) of a utensil (1).
 3. Safety tool according to claims 1 and 2, characterised by the fact that along with the intermediate safety hook (6), there is an inclined plane spring (7) for raising the hook (6), with the end (41) of the holding clip (4) that acts upon the surface of the spring.
 4. Safety tool according to previous claim 3, characterised by the fact that al least one intermediate safety hook (6) is positioned between the flat reference surface (22) of the utensil (1) support body (2) and the lower end (412) of the holding clip (4), and partially acted upon by the spring (7) for raising the hook (6).
 5. Safety tool according to the previous claims, characterised by the fact that at least one hook (6) is made up of a monolithic body and that foresees: two symmetrical spikes (61) along the upper side, that stick out and face the holding clip (4), and which temporarily act upon the holding clip (4) by sitting inside the groove (413) formed along the respective upper tooth (411); and a body (63) facing the same side which supports, in a straddling fashion, the spring (7), leaving a certain amount of space between the two surfaces; while on the opposite side, that is, on the surface of the intermediate safety hook (6) facing the surface (22) of the utensil (1) support body (2), transversally and in correspondence with lower edge, there is a main tooth (62); a secondary tooth (65); and a further tooth (66) that co-operates with a portion of the holding clip (4).
 6. Safety tool according to the previous claims, characterised by the fact that the main tooth (62) of the hook (6) has a flat reference and lifting surface (621) and an inclined leading surface (622) for lateral movement.
 7. Safety tool according to the previous claims, characterised by the fact that the intermediate safety hook (6) has a seal (64) partially inserted in a seat (641) on the side facing the surface (122) of the shank (12) to be clamped.
 8. Safety tool according to the previous claims, characterised by the fact that the spring (7) for lifting the hook (6) has a “V” conformation, the said spring (7) being made of spring steel which partially overlaps and joins, by straddling, a corresponding male protrusion (63), which serves as a body, transversally formed into the intermediate safety hook (6), and that between the said spring (7) and the back (63) of the hook (6) there is a certain amount of play, so that the spring (7), when acted upon by the tooth (412), is deflected in a controlled manner.
 9. Safety tool according to the previous claims, characterised by the fact that the clamping unit joined to the upper beam of a utensil (1) in a press-bending machine is made up of an intermediate set (A) made up of a utensil (1) support body (2) with an attachment (21) to the upper beam of the press-bending machine on the upper side, while the lower part of the said intermediate body (2) has a vertical reference plane (22) along which, in taking up the utensil (1), the corresponding flat surface on the side (121) of the shank (12) is positioned.
 10. Safety tool according to the previous claims, characterised by the fact that the intermediate body (2) has a pneumatic chamber under pressure (23) which pushes and draws back a piston (3) with a perimeter seal (31), the said piston (3) being used to act upon the upper end (42) of a holding clip (4) which, by means of jointed screws (5), is hinged to the intermediate body (2) to transfer the push of the piston (3) to the lower end (41) of the holding clip (4).
 11. Safety tool according to the previous claims, characterised by the fact that the lower end (41) of the holding clip (4) has at least two longitudinal parallel teeth (411) and (412) turned to the same side, the first of which, the upper tooth (411) having a groove (413), on the inside of which the upper portion (61) of at least one intermediate safety hook (6) is inserted.
 12. Safety tool according to the previous claims, characterised by the fact that the second tooth (412) of the holding clip (4) coincides with the lower edge of the of the holding clip (4) and is similar to a half round lip which sticks out towards the surface (22) of the body of the intermediate body (2).
 13. Safety tool according to the previous claims, characterised by the fact that the holding clip (4) has a catch (414) to which the tooth (66) of the intermediate safety hook (6) is temporarily hooked.
 14. Intermediate (A1) with a multiple attachment for utensils, characterised by the fact that it has two mirror-image safety tools according to the previous claims mounted on the front or the back, with each mechanism including at least one holding clip (4) for each side of the upper beam, and which acts upon at least one corresponding intermediate safety hook (6) by means of a spring (7) positioned between for lifting the hook, and joined to the said intermediate safety hook (6).
 15. Intermediate (A2) with a mixed attachment for utensils according to the previous claims, characterised by the fact that only one side has a safety tool according to previous claims, while on the other side there is a mechanical holding system by means of a gripping plate on the shank (12) and fastened by at least one screw to the intermediate (A2).
 16. Intermediate according to claim 15, characterised by the fact that the mechanical gripping plate for the shank (12) is joined to the intermediate (A2) by means of at least one screw that is accessible through a hole on the fastening side of the holding clip (4).
 17. Intermediate (A3) with attachment to the upper beam that is axial with respect to the load axis of the utensil (1), characterised by the fact that there is a safety tool according to previous claims on one side with a holding clip (4) that acts upon at least one corresponding intermediate safety hook (6) by means of a spring (7) for lifting the hook positioned between, and joined to the said intermediate safety hook (6).
 18. Utensil mounted on intermediates according to the previous claims, characterised by the fact that it is made up of a metallic body that forms the punch (11) that presses against the sheet of metal at its lower end, while there is a shank (12) at the top end with a groove (122) that is “C”-shaped (13) if seen in section along at least one side, and in which the shank (12) of the utensil (1) is not in line with respect to the load axis.
 19. Utensil mounted on intermediates according to the previous claims, characterised by the fact that the utensil (1) is of the standard type with a safety groove (13).
 20. Utensil mounted on intermediates according to the previous claims, characterised by the fact that the utensil (1) is of the type with a mirror-image double groove (13), each one along the respective side (121, 122).
 21. Utensil mounted on intermediates (A3) and (A4) according to at least one of the previous claims, characterized by the fact that there is a shank (12) symmetrical with the load axis with, along at least one corresponding side, a groove (13) as a safety feature. 